This invention relates to tip valve assemblies for a pneumatic tool, and specifically to a trigger-actuated, tip-type air valve with an integrated wear surface.
Certain power tools are pneumatically controlled. Tip valves for restricting and controlling the air flow for these pneumatic tools are known in the art. For example, U.S. Pat. No. 4,258,799 discloses an inlet control valve for a pneumatic tool having first and second valve members that are independently moveable. The first and second valve members provide restricted air flow and full air flow.
The prior art includes improved tip valves of relatively simple and economical construction. FIG. 2 shows the tip valve of U.S. Pat. No. 6,027,099 (“the '099 patent”) in the closed position. U.S. Pat. No. 6,027,099, which is also owned by Snap-on Incorporated and is incorporated herein by reference, discloses a tip valve for a pneumatic tool including a first valve member having a bore (to allow airflow there through) with a central axis and defining a valve seat about the bore and a second valve member having an engaging surface engageable with the valve seat to form a substantially fluid-tight seal therewith. A stem is coupled to the second valve member and extends through the bore, with at least a portion of the stem being offset from the axis, and a valve operating member is coupled to the stem for movement between a closed position wherein the second valve member engages the valve seat to close the bore and an open position wherein the second valve member is tilted from the valve seat to open the bore to permit air flow. A spring urges the second valve member and the valve operating member to the closed position.
U.S. Pat. No. 7,032,881 (“the '881 patent”) discloses a switch mechanism for a pneumatic tool including a trigger and a tip valve. As seen in FIG. 4 of the '881 patent, the device includes a bushing 60 with an annular shoulder portion 62. This bushing 60 is disposed between elements identified as a choke member 50 and a choke ring 30. The choke portion 51 presses against an abutting portion 61 of the annular shoulder portion 62 of the bushing 60 instead of pressing against the inner wall of the air passage 21. The bushing 60 is made of a harder material than the choke member 50 so that the choke member 50 will be worn before the bushing 60.
In this regard, it is important to have an integrated wear surface to protect the air channel, i.e. a cylindrical wall, or other components from wear. Based on durability, components can be constructed of different materials. Also, in certain circumstances, it is desirable to have minimal internal rotation of the second valve member of the tip valve.